Control devices for the automotive field are generally used to control and monitor functions of the vehicle engine and/or additional electrical systems in the motor vehicle. Such a control device may be equipped with a non-volatile memory in order to store various performance quantities and the like on a permanent basis, i.e., even when no supply voltage is applied, so that the control device can access data from the past as well.
The demands on the components used in the automotive field are very high, however, and in most cases require extremely high reliability during the entire service life of the motor vehicle. The demands on the non-volatile memories used in automotive control devices are therefore high as well. In general, flash memories are utilized as non-volatile memories for automotive control devices. Because of the degradation effects of the flash memory cells, the service life of a flash memory cell is limited to a specific number of write cycles. The manufacturer usually guarantees a specific number of write cycles for a flash memory for a specific overall operating period of the motor vehicle during which said control device is operated.
In an effort to reduce the frequency at which a specific memory cell of the non-volatile memory is overwritten in a control device, the size of the memory in the control device is increased and performance variables to be stored therein are written to the memory sector consecutively. If one memory sector of the memory, i.e., one segment, is filled up with performance quantity data, then the most recent performance quantity data of each type are copied to another segment in a reorganization process, and the completely written segment is erased in an erase operation immediately following or prior to a new write operation.
During the reorganization of the data, a search for the most recent performance quantity data of the completely or virtually completely written segment is implemented at present, which are then written byte-by-byte to the corresponding next segment that subsequently is to be written with performance quantity data. Furthermore, performance quantity data from a working memory of the control device, i.e., a write/read memory, which usually stores data in a volatile manner, such as a RAM, may be written to the additional segment in the reorganization of the data, i.e., a resorting of the data, for example, these data from the working memory likewise being written to the additional segment in a byte-by-byte manner. Since the writing of each byte requires a separate access operation to the non-volatile memory, the reorganization of the data in such a memory system takes time and effort.